Thermoelectric generator



H. G. PACK THERMOELECTRIC GENERATOR Nov. 2l, 1950 2 Sheets-Sheet 1 Filed April 5, 1948 INVENTOR.

5 M Dm. vf G M7 Nv t Nov. 21, 1950 H. G. PACK THERMOELECTRIC GENERATOR 2 Sheets-Sheet 2 Filed April 5, 1948 Knnnnn (Hl INVENTOR. Herschel Cl, Pack' Patented Nov. 21, 1950 UNITED STATES PATENT OFFICE THERMOELECTRIC yGENERATOR Herschel G. Pack, Bakersfield, Calif.

Application April 5, 1948, Serial No. 18,877

6 Claims.

This invention relates to thermo-electric generators and more specifically to a device of this type that utilizes new and novel means for the generation of electrical energy. In my co-pending application, entitled Thermo-Electric Generator, Serial No. 752,658, which was filed on June 5, 1947, I have described a thermo-electric generator utilizing movable heat transfer members positioned between the positive and negative elements for generating electrical energy. The primary difference between this invention and the reference 'invention is that I utilize liquid metal to replace the movable heat transfer elements shown therein. In the reference invention I explain how a third metal could be used between a positive and negative element to provide the heat required for thermo-electric generation in that the third metal was itself positive to one and negative to the other. I have found from experiments that molten metal acts exactly the same electrically and provides many advantages asa heat transfer element.

The principal objective of my invention was to construct a thermo-electric generator capable of continually generating a heavy electrical current and using an electrical .conducting liquid for the efficient conduction of heat and for making an electrical connection between the positive and negativeelements or plates of the thermocouples.

A further objective was to design such a generator which would have greater efliciency than heretofore obtained by similar devices.

In the preferred embodiment of my invention I provide a series of thermocouples with means for retaining an electrical conducting liquid between the elements of the thermocouples.

` I further provide means for circulating hot and cold liquids in said electrical conducting liquid for the purpose of creating hot and cold junctions.

Further objectives and advantages of my invention will be apparent as I proceed with the description.

With reference to the drawings- Fig. 1 shows an end elevation of the preferred form of my invention partially in section;

Fig. 2 shows a sectional view on line 2-2 of Fig. 1;

Fig. 3 shows a sectional view on line 3-3 of Fig. 1:

Y Fig. 4 shows a modication of my invention acting as a. primary winding of a transformer;

i Fig. 5 shows an enlarged sectional view on line i-Uof Fig. 4; and

Fig. 6 shows a practical application of my invention. p

In Figs. 1, 2 and 3 I show the preferred form of my thermo-electric generator A which includes a plurality of thermocouples II in electrical series. Each thermocouple Il consists of positive and negative elements l2 and I3 which are in the form o f flat metal sheets. Any desired metals may be utilized so long as they are dissimilar thermo-electrically. The elements I2 and I3 are relatively thin having, however, a large cross-sectional area. The surface of the elements l2 and I3 are roughed or etched in order that a greater area might be exposed to the liquid medium. I have found that by having one element made of iron and the other of Monel very satisfactory results are obtained.

As shown in the drawings, the positive and negative plates l2 and I3 are spaced from each other and are maintained as a compact unit through apertured blocks I4 made of ceramic or other similar insulating material. It is imperative for the proper functioning of the generator A that these units be airtight and that the cavities or spaces I5 between the positive and negative elements be airtight in order to prevent oxidation of the plates and liquid medium. The cavities l5 between the plates I2 and I3 are preferably lled with sodium I6 which has a low melting point and is eminently satisfactory for this purpose, having excellent thermal conductivity properties in addition to its ability to make instantaneous electrical contact. In each cavity I5 is positioned a coil of tubing I1 with alternate cavities being connected to one system of tubing I9 and the other cavities being connected to another system of tubing 20. Through the first system of tubing I9 is circulated a heated medium which. is maintained in a heated state by the burner 2| positioned below the reservoir 22. Through the other series of cavities is circulated a cooling medium which is pumped from a reservoir 23 and is circulated through the system 20 by the pump 24. The coil systems I9 and 20 through which the fluid will be circulated must also be airtight. In addition, rubber insulation 25 is provided to prevent short circuiting of the elements. It is also necessary that the fluids that are to be circulated in these tubes are reasonably good electrical insulators, and any one of a number of uids that are known and used for heat transfer may be utilized.

With reference to the metal plates I2 and I3 it is important that the metal does not have too low a melting point, Since the electromotive tion, a heated fluid will be circulated through g;

some of the tubes of the sodium-filled cavities while through alternate cavities a cooling fluid is circulated to absorb the heat conducted through the elements and the sodium barrier. ,This arrangement then provides the hot and cold 'junctions of a thermocouple which are necessary to generate the electricity. The sodium in the hot section will melt in view of the Afact that it 'has a very low melting point and the sodium in :the

cold section may be either solid or liquid depending on itstemperatureand.co u1d in fact Vbe a block of lead or other solid metal throughwhich thecooling fluid would. circulate. .Sodiurnisfpreferable, vbecause it is vnot onlyan .excellent conductor of heat and electricity, ibut it is light in weight. As stated, a generator comprising va series of-such elements .would deliver a very heavy steady current .due to its flow ohm'ic resistance and operating characteristics. .Its direct efdciency would vnot be .very high, since most of the heat is carried .off Yby the cooling iiuid, but this heat'lis in a vconvenient form to .be utilized again either ,for 'further electrical generation or other heatingpurposes, and 'thereforepmeans are provided for generation of Avery heavy currents where eic'iency .is of 4secondary importance. n

'In Fig. '5 I show a modication' of my thermoelectrc generator consisting of two vspaced positive and negative elements '3| and 32 Yseparatedas'previously described vby a ceramic ring 33. .Itis preferable that the space or cavity 34 between'the platesbe evacuated or 'lled with an inert gas of low pressure. 'The'latter is ,preferable, "because it provides a cushion or spring against which the' liquid metal 35 Vis forced and the recoil willexpedite the .return ofthe metal to the reservoir 36. 'The Aconnecting tube 31 between the Vcavity and the reservoir would be short and `of'large cross sectionalarea. vA piston 29 andpump38 would be used to 'force'the liquid metal up intothe'cavity. The reservoir'36 would be 'heated "by ajgas burner '33 or other conventional means lto maintain the liquid Ymetal preferably sodium in a heated stated. jin operation,

when the heated metal'is forced upinto'the cavity 34, a difference of electrical potential willbe developed 'between 'the vouter surfaces of the dissimilar metal elements .3| and '.32 which are o'f iron andMcne'l metal .respectively .and will continue at a diminishing rate as the elements approachthesame temperature. Mercuryimay also be 'usedg because 'itisliquid at normal temperatures and may be heated to a considerablyhigher temperature. jAs ,soon as 'the voltage has'dropped to a 'low'valua the metal Acan'be withdrawn and heated again.and `the cycle repeated. 'In fact, it might not even'be necessary to remove Lthe metal as the cavity maybeconnected'bya short tube 3'! .of large cross .sectional area to a reservoir ofheated liquid to which heat-is continually* applied, and-the dissimilar metal vsheets may vbe increased in thickness or'be cooledby some lother meansso that continuous .generation results.

, klnfFig. 4 lI have shown this latter modication tammy-:invention utilized .in conjunction with-a 42 of many turns. The thermocouple 3|) may then be inserted into the opening of the primary winding 4|, and the liquid metal 35 may be pumped up into the cavity 34 between the metal plates 3| and 32 by the piston 29 and pump 38. As the metal is heated, a thermo-electric voltage will be generated when the metal is between the plates andinterrupted whenthemetal is withdrawn. It can further be--seen that the making and breaking of this small voltage will result in an alternating voltage much higher across the terminals of the secondary coil 42. This is analogous 'to the system used in automobile radios .wherea .vibrator is used to make and break the low direct current battery voltage to produce an 4alternating current of relatively high voltage.

Dueto the low ohmic resistance, the current in the single turn 4| is very high and means have been provided ,for interrupting vor vVarying a heavy current with the riseand-fall of the liquid metal. This system alsofprovidesa means for converting the low voltagetof a thermocouple fintoan alternating voltage commensurate with ,thatof other' electrical systems. Itis, of course, evident'ithat ahumbercf .such units could operate on a commonironcore or lonseparatecores and the pulsing be timed 'to obtain whatever electricalf're--4 quency is desired. 'The sectional electricalrconnectionsmay be arranged as in any other Aelectrical system. Since this device provides Ameans foi-switching Ya very heavy current, it could be placed at one point in .the single turn ,coil and the remainder of `the turn connected to one of` the `multiple element steady current generators previously described. Then the voltage wouldy be .interruptedju'st as for one thermocouple. y

In Fig. V6 I have shown a suggested arrange-l ment 'for converting heat into mechanical` energy by using 'the pulses of electriccurren't to alternate'ly attract an'drelease the armature 5D. As shown in the ,draw'ingan ,.iron. c0re15.| `has .positionedaround ita winding '.52 consisting of one heavy turn of wire. The un'it 30 shownin Figs. 4 andj5 is ,positionedinithe opening ,of the winding 52 and as the molten `metal is alternately pumped in'to and withdrawn from the -cavitya pulsating electrical current .will be generated which will cause 'thearmature-tobe attracted to the iron core 5| `and which when the circuit isbroken will be Vdrawn .backy into position bythe spring-53. The .armature is shown connected `to a flywheel 54 through acrankv55 and when in operation depending upon the `frequency of the pulsating rcurrenttlfie flywheel will vbe caused t0 rotate. V

.Although I have setforth `the most satisfactory materials .for `the leiiicie'nt voperati/on of `my ,ther--l ino-electric generator, it is realized that the thermocouplerelements need ,not be metal `and .that any twoelectrical conductorsthatmay be heated would serve the purpose such as carbon .andsilicon carbide. Also.that-,anymaterial.thatbecomes a fair conductor in .the ,molten state/such assalts e. g. sodium hydroxide mayfbe .used as the conducting material "between :the elements of .'the thermocouple.

While the invention hasbeen described inde; tail with ^respect to a present preferred form which it may assume, it is not to be limited to such details and form since many vchanges and modifications mayibea-made inthe -inventionrwithout departingfrom the vspirit and scope lof Lthe invention in its broadest aspects. ifHence,it is 5 desired to cover any and all forms and modications of the invention which may come within the language or scope of any one or more of the appended claims.

I claim:

l. A thermo-electric generator including a casing divided into a series of chambers by spaced partitions of thermo-electric material having predetermined thermo-electric relative values, a conductive liquid in each chamber, means for heating the liquid in alternate chambers, and means for cooling the liquid in other alternate chambers.

2. A thermo-electric generator including a casing divided into a series of chambers by spaced partitions of metal alternately positive and negative, conductive liquid in each chamber, a source of heating liquid and pipe connections from said source to every other chamber to heat the liquid therein, a source of cooling liquid and pipe connections from said latter source to the intermediate chambers to cool the liquid therein.

3. In combination with an electric transformer having a core and a secondary winding thereon, a primary winding around said core and having free ends, a thermo-electric couple associated between said free ends, and means for alternately introducing to and withdrawing heated conductive liquid from between the elements of said couple.

4. In combination with an electric transformer having a core and a secondary winding thereon, a primary winding around said core and having free ends, a pair of plates forming a thermoelectric couple connected to and disposed between said free ends, and means to alternately intro- 6 duce heated conductive liquid between said plates and to withdraw the heated liquid therefrom.

5. In combination with an electric transformer having a core and a secondary winding thereon, a primary winding around said core and having free ends connected to a chamber, spaced walls of said chamber formed by thermo-electric plates, a source of heated conductive liquid, connections from said source to said chamber, and means associated with said source to alternately move liquid through said connections into said chamber and withdraw it therefrom.

6. In combination with an electric transformer having a core and a secondary winding thereon, a primary winding around said core and having free ends, a thermo-electric couple associated between said free ends, and means for introducing heated conductive liquid between the elements oi' said couple.

HERSCHEL G. PACK.

REFERENCES CITED The following references are of record in the iile of this patent:

UNITED STATES PATENTS Number Name Date 375,243 Acheson Dec. 20, 1897 420,764 Bradley Feb. 4, 1890 713,652 Kitsee Nov. 18, 1902 2,425,647 Sarver Aug. l2, 1947 FOREIGN PATENTS Number Country Date 8,985 Great Britain of 1901 111,489 Great Britain June 25, 1918 

